QSAC standardized the measuring system for the restrictor plates. QSAC is using go/no-go Vermont Gage Pins Class ZZ (+/- .005mm) 60 Rockwell Hardness; These are available on page 1392 of the MSC Catalog.
Part #88933304;.3330; 8.4582mm
Also a two head pin handle is available. Part#82931809
Go to mscdirect.com and search by using the part numbers, the page is no longer correct due to new catalogs.
I just looked all of them up, total price for 4 pins and two holders, $46.50, plus shipping.